dzhokhar tsarnaev, the 19-year-old bombing suspect remains in serious condition where he is recovering from his wound, but apparently he is alert enough to begin responding to some of the investigators' questions. many of those responses in writing because he has gunshot wound possibly, self-inflicted to the throat, but amazingly, he and his brother for some three days managed to hide in plain sight. dzhokhar at umass dartmouth where he was a student, he worked out in the gym, even talked to friends about the bombing. imagine how chilling that was for his classmates. >> i'm in diss belief, like, i can't believe that's him. >> i don't want to believe it. >> i really don't. >> we saw his image and we don't want to believe it was him. >> it totally looked like him. we thought it was a mistake or, like, a joke or something. >> reporter: well, all of it changed, of course, on thursday, late afternoon when authorities released the pictures of the two brothers and a grisly manhunt began that resulted in the deaths of an m.i.t. campus police officer and serious injury to a boston transit cop a